1. Field of Invention
This invention relates to a method for correcting optical aberrations in the optical system of an eye having an intraocular lens. More particularly, this invention relates to a method of correcting optical aberrations and other focusing abnormalities measured by wave front or other such technology to quantify optical aberrations in the optical system of the eye, using a laser, or other apparatus and/or methods of fabricating or modifying a lens, for the optical system of an eye having an intraocular lens.
2. Description of Related Art
The field of refractive surgery has been evolving rapidly during the past few decades. Unfortunately, the current procedures or methods used by most refractive surgeons may not ultimately satisfy the total refractive needs of the patient. Particularly, the most commonly performed refractive surgical procedures, such as, for example, cataract extraction with intraocular lens implantation, in addition to the most recently popularized corneal refractive surgical procedures, such as eximer laser photoblation, have a number of drawbacks and limitations A reason for some of these drawbacks and limitations is the fact that the lack of post-operative refractive accuracy renders these surgical procedures uncompetitive with the already available non-surgical alternatives available to patients, which are commonly known as glasses and contact lenses.
Current refractive cataract surgeons who perform the most common refractive surgical procedure, i.e., routine cataract surgery, demonstrate refractive accuracies in the xc2x10.75 to xc2x11.00 diopter (D) range. However, such a refractive accuracy is generally not satisfactory, given an industry established accepted accuracy goal of xc2x10.25 D. Furthermore, several recent reports analyzing current corneal refractive technologies indicate the presence of a significant amount of preexisting or naturally occurring post-operative, as well as preoperative, image distortion (optical aberration) or degradation, particularly under low light conditions, such as when driving at night.
Because of surgery, as well as the biological and physical behavior of the human eye during and after the various types of intraocular surgery, the predictability at the xc2x10.25 D level with just a single surgical procedure is virtually impossible 100% of the time. Furthermore, factors like biometry errors, variable wound healing and capsular contraction around the intraocular lenses all contribute to decreasing the ability of the refractive surgeon to be able to achieve the desired refractive accuracy. Accordingly, practitioners in the industry have found that an adjustable intraocular lens (IOL), hereinafter referred to as the MC-IOL (multi-component) or C-IOL (compound), following lens extraction surgery, provides a number of desirable options for the refractive surgeons as well as their patients.
First and foremost, an adjustable IOL allows fine tuning of the initial refractive result by exchange of several optical elements of the lens implant. Accuracies in the xc2x10.25 D range should be virtually guaranteed for those patients which demand perfect vision. It is very likely IOL technology will continue to evolve in the future. Therefore, it is desirable to provide the patient with the opportunity to undergo an exchange of xe2x80x9coldxe2x80x9d technology lens components for the new and improved technology. This can only happen if the surgeon has an effective, efficient, and sale method of performing lens element exchanges. Additionally and more importantly, within the months and/or years after any refractive surgical procedure, if the optical properties of the inserted IOL, such as multifocality for example, becomes problematic, the surgeon has the ability to safely exchange the undesirable optical elements of the IOL to reverse or eliminate any optical problems that are not tolerated by the patient.
In 1990, the inventor of this application began to investigate the feasibility of such an adjustable intraocular lens, commonly known as the multi-component intraocular lens, hereinafter referred to as the MC-IOL (FIG. 1), for use following clear lens or refractive cataract surgery, wherein the optical properties of the MC-IOL can be modified at any post-operative time. The base intraocular lens component of the MC-IOL is shown in FIG. 1. The cap (mid) lens attaches to the top of the base lens and holds the third component of the MC-IOL, the sandwich (top) lens, in place as well.
The base intraocular lens 10 and cap 20 each have securing flanges 16, 18 and 20, 24, respectively, extending therefrom. The MC-IOL also comprises at least one sandwich lens 30), as illustrated in FIG. 1. The sandwich lens 30 is positioned on top of the cap 20. See FIGS. 1-2.
The MC-IOL also includes projections 11 and 13 which serve to hold the MC-IOL in place in the human eye, wherein eye tissue (lens capsule) takes hold on the projections. This arrangement permits the base intraocular lens 10 to form a platform upon which the cap 20 can be placed to provide a vehicle to hold the sandwich lens 30. Therefore, during routine cataract surgery, the MC-IOL replaces the crystalline lens of the human eye. Once a patient""s eyes have healed after such a surgery, the surgeon can reenter the eye and replace, if necessary, and more than once, the sandwich lens 30 and the cap 20 to modify the optical characteristics until they reach desired levels.
FIGS. 3A-3B illustrate the assembled compound intraocular lens, hereinafter C-IOL, that can be used with a preexisting lens within the human eye. The C-IOL has two components similar to the cap (mid) FIGS. 4A-4B and sandwich (top) FIGS. 5A-5B lens components of the MC-IOL. The preexisting lens can be the crystalline lens of the eye with the C-IOL placed in the sulcus (FIG. 6) or in the anterior chamber angle (FIG. 7). However, the C-IOL can also be used with a conventional IOL and be mounted in the sulcus (FIG. 8), in the anterior chamber angle (FIG. 9), in the anterior chamber with posterior chamber fixation (FIG. 10) or in the anterior chamber with iris fixation (FIG. 11). Thus, a surgeon modifies the optical characteristics of the optical system of the eye by using the cap and sandwich lenses in tandem with the preexisting conventional IOL implant or the crystalline lens of the eye.
A single component, exchangeable (adjustable) anterior chamber lens can be used in combination with a single component posterior chamber lens. (FIG. 12). This enables the adjustment capability for one of the two components and allows more latitude with respect to the space available in the anterior chamber. Both single component conventional nonadjustable anterior chamber and single component conventional nonadjustable posterior chamber refractive intraocular lenses are currently being used with success. In this lens design however, the exchangeable element of the anterior chamber lens component is unique. Finally, the separation of the two lens components might allow an additional refractive capability such as telescopic vision. This might also necessitate the use of either an additional corneal contact lens or spectacle lens or both.
The C-IOL and MC-IOL provide numerous enhanced features. For example, the C-IOL and MC-IOL can each be structured as a monofocal or multifocal optical system, correct astigmatism, as well as comprise ultraviolet light-absorbing, tinted, or other such chemically treated materials.
It should be understood that there are various reasons why an adjustable, MC-IOL or C-IOL is more desirable than a single component implant. In order to achieve all of the permutations and combinations of the astigmatism, multifocality, and spherical correction needed to achieve emmetropia would take an inventory of over ten thousand lenses, whereas with the MC-IOL (multiple components) concept, an inventory of about one hundred components would be necessary. With anterior chamber lenses, progressive encapsulation or engulfment of the lens haptics by uveal tissue in the angle often occurs 1-2 years post-operatively, making removal difficult or impossible. Exchange of iris fixated anterior chamber lenses cannot guarantee precise position or orientation. Posterior chamber lenses similarly cannot be removed because of posterior capsule fibrosis. Easy removal and exchange ability is critical for any customized emmetropic system. Only a specially designed multicomponent lens system allows this.
Therefore, based on the above discussion, a MC-IOL having three elements rather than one permits refractive customization and adjustability for all refractive errors, for all patients, using a minimal number of lens elements or parts and requiring little customization required by the manufacturer. Thus, it has become very important in the refractive surgery art to be able to individualize and/or customize surgery such that the surgeon can easily and safely, as well as accurately, modify the refractive power of an intraocular lens implant.
For an example, U.S. Pat. No. 5,288,293 to O""Donnell, Jr. discloses a method of modifying a single IOL. O""Donnell suggests that the refractive power of a single IOL may be varied before implantation so that the changes can be made in situ by the ophthalmologist after determining the extent of correction required to improve the vision of the patient before the lens is made. However, the surgical implantation procedure itself may create additional optical aberrations which cannot be anticipated preoperatively and thus not accounted for in the primary lens implant.
As such, it may be argued that if a lens can be modified before being implanted, as suggested by O""Donnell, Jr., it should be possible to modify the implanted lens by removing the implanted lens, modifying the lens, and then reimplanting the modified lens into the optical system of the eye. However, although one may theoretically be able to take a lens that is already implanted into the optical system of this eye, remove the implant from the optical system, modify the implanted lens and re-implant the modified lens as suggested by O""Donnell, unfortunately, IOLs are not designed to do this very easily. Furthermore, after a period of time with normal healing, it will become physically dangerous and/or nearly impossible to the patient to accomplish this once the eye tissue takes hold on the capsular fixation holes of the lens. Therefore, such an argument, although theoretically possible, in reality is not practical or safe. A single component intraocular lens, which in general is not designed to be removed and with only two optical surfaces, cannot allow for compensation of sphere, cylinder, cylindrical axis, and all forms of optical aberrations that may be discovered after the initial implantation. Whereas, the multipart IOL will have four removable optical surfaces which could compensate quite adequately for these optical properties.
The inventor of this application invented the previously discussed MC-IOL and C-IOL that are designed specifically to permit the easy exchange of optical elements at a post-operative period without risk to the human eye or the patients beyond that of ordinary intraocular surgery. The easy exchangeability of optical elements is critical because the actual surgery of implanting the lens in the first place, as well as the way the eye might heal after implantation, does create distortion which may not stabilize for several months after the operation. Therefore, the ability to measure and to compensate for that distortion cannot take place until several months after the actual surgery has occurred and could not be predicted prior to the actual surgery occurring. Since the same surgical wound is used for both the primary and secondary operations, additional distortion due to wound healing would not be anticipated as a result of the second operation. Furthermore, the ability to exchange optical elements of a multicomponent or compound intraocular lens can be quite economical compared to removing, modifying, and re-implanting a single component lens, as well as easier to perform.
The MC-IOL has four surfaces available for modification, two piano and two convex. While it is possible to modify any of the four available surfaces, it is preferred that the modification be made only to the piano surfaces. This will avoid interfering with the convex side which may already be used for correction of astigmatism (cylinder) or used as a multifocal lens surface. The same statement applies to the CIOL which has two surfaces available for modification, one of which is piano and the other convex.
It is an object of this invention to overcome the above-described drawbacks of the related art.
In particular, it is an object of this invention to conduct measurements using existing technology, such as wave front analysis, to determine any residual or new aberrations that are present in an operated eye after the biological healing parameters have stabilized as well as to correct any residual errors in sphere, cylinder or cylindrical axis. Then, the surgeon will be able to go back into the eye through the very opening that was first created to position the implant and modify one, two, or even more existing lens elements within the implanted optical system based on the measurement obtained from the wave front and refractive analysis. Such modifications will preferably be accomplished with a laser, such as an excimer laser or other known or later developed means suitable for creating an optical surface.